1. Field of the Invention
The invention relates to a cooling and holding body for heating elements, in particular PTC heating elements or flat heating panels, a heater having such a cooling and holding body and a method for the manufacture of such a cooling and holding body.
2. Description of the Related Art
In control cabinets, for example, temperature changes cause the formation of condensate which, together with dust and aggressive gases, can cause corrosion. The risk of breakdowns due to leakage currents or flashovers increases as a result. Heaters or fan heaters, in particular PTC semiconductor heaters, which are subject to high requirements in terms of reliability and longevity, are therefore used to ensure consistently optimum climatic conditions for perfect functioning of the components located in the control cabinet.
Such heaters are usually fitted with electric heating elements. The holding device of these heating elements should enable good heat transfer on one hand and consistently secure fixing on the other. The frequent and, depending on the operating conditions, major temperature changes can lead to material fatigue due to aging and therefore to a decrease in the holding force with which the heating elements are fixed. The heat transfer deteriorates as a result. If the holding function is lost completely, the result may even be a total failure of the device.
DE 196 04 218 A1 describes an example of a known heater with a PTC element in which the PTC element is mounted in a rectangular recess arranged centrally. A double wedge arrangement which can be moved by means of an adjusting screw in order to alter the width of the double wedge arrangement is provided in the recess for mounting. The PTC element can therefore be jammed in the recess. The double wedge arrangement is complex and does not eliminate the problem of the decrease in clamping force due to material fatigue. The double wedge arrangement would have to be adjusted by manipulating the screw in order to prevent this.
An improvement of this known device is disclosed in DE 2006 018 151 A1 which refers back to the applicant. In this case, the heating element is disposed in the centrally arranged recess of a heat exchanger, wherein the inner contact surfaces of the recess lie flat against the heating element. The holding force is achieved in that, after installation of the heating element, side walls of the heat exchanger are bent inwards which reduces the gap between the contact surfaces of the recess. The heating element disposed between the contact surfaces is firmly clamped flat as a result. This fastening is a stable holding device which delivers a constantly high holding force and therefore constantly good heat transfer from the heating element to the heat exchanger without readjustment. Bending in of the side walls, however, leads to a plastic deformation of the wall material which is not optimal for the holding conditions because of the frequent temperature changes.